Progesterone modulation of specific protein synthesis in the decidualized hamster uterus

Progesterone-dependent synthesis of specific proteins was studied on Days 6, 7 and 8 of pseudopregnancy in the decidualized hamster uterus. Progesterone withdrawal was induced by removal of subcutaneous steroid implants from ovariectomized animals; hamsters retaining the implants served as controls. Eight hours after hormone withdrawal, myometrial and deciduomal tissues were labeled with [³⁵S]methionine during incubation for 1 h in vitro, and proteins were separated by two-dimensional gel electrophoresis followed by autoradiography of the dried gels. Analysis of the two-dimensional gel patterns (maps) revealed both increases and decreases in autoradiographic spot intensity comparing progesterone-withdrawn samples to controls, indicating that progesterone both suppressed and stimulated gene expression in the decidualized uterus. Protein synthesis in the deciduoma was more responsive to hormone withdrawal than that in the myometrium; e.g., 45 changes on Day 7 vs. 26 changes, respectively. The sets of proteins in each tissue responding to progesterone withdrawal through changes in synthesis have been termed 'domains'. The progesterone domains shifted from day to day during decidualization in size and degree of overlap (changes in protein synthesis common to the domain on different days). Although the degree of overlap was similar in cytosol from both tissues, marked differences were apparent in the overlap of responses in the nucleus. Overlap was extensive in the deciduomal nucleus where six protein spots increased intensity following progesterone removal on each day. In contrast, little overlap was seen between the progesterone domains in the myometrial nucleus. These findings emphasize the differences between these two tissues in their responses to progesterone withdrawal, yet five proteins (one cytosolic, four nuclear) responded similarly to hormone removal in both tissues. These studies show that: 1) progesterone domination of the uterus during pseudopregnancy alters synthesis of many proteins in both the deciduoma and myometrium; 2) progesterone effects on specific protein synthesis during decidualization occur in both positive and negative directions; 3) the proteins modulated by progesterone and, by extension, the genes affected by this hormone are predominantly different in the deciduoma and myometrium, and 4) progesterone modulation of specific protein synthesis in the decidualized uterus is time-dependent, such that the domains of response vary daily in composition, size and overlap.